Sunday, October 28, 2018

Season 13 superfinal, games 21-30

After 30 games Stockfish leads 4-0 with 26 draws.
The draw rate is high at 86.7%, Komodo is defending better than I expected but it still hasn't been able to find a win.

Evals were close to 0 in game 21. There were many early exchanges that left RN vs RN on move 26. The game was adjudicated by draw rule once the pawns stopped moving. In game 22 the exchanges were delayed until move 22, but then a series of exchanges resulted in a knight ending on move 32. This time the game ended in a tablebase draw.

Games 23-24 started with a Latvian opening, and in both games the engines played a line where white wins a rook for a knight. In game 23 Komodo pushed two central pawns forward, and one reached the 2nd rank protected by a bishop. Evals were at 0 despite the material difference, exposed kings and open position. The engines exchanged down to a RBN vs BBN position, the advanced pawn compensated for the material advantage and the game was adjudicated a draw. In game 24 Stockfish gave a bishop and was a full rook down, with a strong attack on the white king while Komodo's queen was far. Amazingly evals were 0 in this wild position. Komodo gave the rook back and exchanged pieces to get its king out of trouble, and then ended the game with perpetual check.

Stockfish started game 25 with an eval of 1. Komodo cleared most white pawns on the queen side and exposed the white king, the evals came down. The engines exchanged down to a QRN vs QRN position and the game ended by repetition on move 31. In game 26 Komodo had a small eval advantage from the start. Stockfish gave a rook for a knight early, the engines castled in opposite directions and both pushed pawns facing the opponent's king. The position opened up and most pieces were exchanged. The game reached a RB vs BN ending with only one black pawn. The position was a 7-man draw, it took the engines more than 50 more moves to accept the result.

There were many early exchanges in game 27, and only RRB vs RRB were left on move 26. Evals were at 0 for the rest of the game, ending in a tablebase draw. In game 28 there were again early exchanges and only RBB vs RBN remained on move 22. Komodo was hopeful for a while but the game reduced to an opposite color bishop ending. Komodo was a pawn up but not enough for more than a draw.

Stockfish started game 29 with an eval advantage under 1. It pushed pawns on the king side, creating a space advantage while leaving its king a little exposed. Most pawns remained on the board and almost all of Komodo's pieces stayed confined behind the pawns. Stockfish pushed a pawn to h6 forcing the black DS bishop to the corner almost trapped.

A few moves later the trap for the black bishop for complete. Evals gradually increased as the engines shuffled for a while and Stockfish opened the queen side. Stockfish's eval was over 4 though material was still equal, Komodo couldn't untangle itself.

Komodo gave a rook to get rid of the strong white LS bishop. The engines exchanged a few more pieces, both evals showed that Stockfish was winning.

Essentially Komodo was playing a rook down at this point, the game was adjudicated before Stockfish won more material.

In the reverse game 30 Komodo kept its king side pawns back. The engines exchanged pieces on the queen side and evals came down to 0. The game reached a BB vs BN position and was adjudicated by the draw rule.